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Post your sub-arc second double star reports here !

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#226 John Fitzgerald

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Posted 07 September 2023 - 04:37 PM

Back on August 19, I had good seeing, and saw a definite split on this one with my 6" f/8 apo at 243x, using a 5mmTV Delite eyepiece.

 

Cyg SAO 68695 RA 19 41 15 Dec +30 43 17 Desig: BU 145 AB, PA 272, Sep 0.85", m 7.4, 9.09.  


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#227 Nucleophile

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Posted 07 September 2023 - 06:18 PM

Back on August 19, I had good seeing, and saw a definite split on this one with my 6" f/8 apo at 243x, using a 5mmTV Delite eyepiece.

 

Cyg SAO 68695 RA 19 41 15 Dec +30 43 17 Desig: BU 145 AB, PA 272, Sep 0.85", m 7.4, 9.09.  

 

That's a fine instrument  you have there, John.  Nice result!



#228 columbidae

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Posted 09 September 2023 - 05:20 PM

From a few nights ago, during yet another hot and hazy night in S. Texas.  

 

BU 472 - 0.75", both mag 8.8

ADS 769 - 0.7", both mag 9.2  (love those even doubles)

BU 155 AB - 0.67", mags 7.4, 8.1

STF 2783 - 0.65", mags 7.7, 8.1

ADS 756 AB - 0.58", mags 8.3, 9.2

 

And, while being the furthest separated sub-arcsecond pair of the night, the most spectacular of them all:

 

HU 765 - 0.8", mags 9.3, 9.6, which combine as the secondary of STF 2764, 7" away from the 8.3 mag primary - a very pretty, well balanced, and close triple!  Very striking with nearly perpendicular PAs and a 10x difference in separation.


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#229 R Botero

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Posted 10 September 2023 - 02:51 AM

Great session Columbidae. I need to check HU765. 
 

Roberto



#230 VanJan

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Posted 10 September 2023 - 11:37 AM

STF 2764/HU 765 - White, bluish, bluish. 11th magnitude companion p, slightly n. 250X  20cm reflector  October, 2022


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#231 Nucleophile

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Posted 10 September 2023 - 11:48 AM

VanJan and Columbidae:  those are some fine targets to try.

 

I also like the Doubles of ~Equal Brightness (DEBs), especially those that cross from Rayleigh at one aperture to Dawes at another--gives me a chance to play around with my on-axis masks.  grin.gif



#232 columbidae

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Posted 18 September 2023 - 07:51 PM

A brighter (and more well-known) duo from last night:

 

44 Boo, STF 1909: 0.47" (est.), mags 5.2, 6.1

Eta CrB, STF 1937AB: 0.57" (est.), mags 5.6, 6

 

Kind of annoyingly bright for close splitting in a 12", but each pair's numerous diffraction rings can't hide the black space in between the spurious disks.  (At least when the whole pattern stopped wobbling for a bit.)  I figured it'd probably be one of the last chances I'd get at the pair this season, so I went for them despite being at the dark site and having a list of other things to go for.

 

If you're a fan of the appearance of double stars in refractors, a sketch of what I saw would probably disgust you, but a split's a split.  axe.gif


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#233 flt158

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Posted 19 September 2023 - 06:25 AM

What are your magnifications for all these wonderful doubles, Columbidae?

I'm sure there are seriously high! smile.gif 

 

Best regards from Aubrey.  



#234 columbidae

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Posted 19 September 2023 - 07:56 AM

Most of my close doubles are split at 381x, with my 4mm eyepiece; it's about 30x per inch in my scope, so high, but not as high as it could be.  I have a cheap 2x barlow (with a 1.5x option) that I sometimes use, but it usually isn't worth the extra magnification.  The seeing is rarely good enough to support 500x and up, and it doesn't work with my coma corrector, which is essential for maintaining good Airy patterns across the field of view.

 

About all but maybe two of the doubles I've split are still above the Rayleigh criterion in my scope, so such a "low" magnification might be a little limiting, but I'll take what I can get. 


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#235 columbidae

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Posted 30 September 2023 - 04:24 AM

Tonight was more of a carbon star night, but there's always a double or two along the way:

 

  • BU182 - 0.73", mags 8.7, 9.1 - "nicely dim, even, with ample space at 381x" 
  • STT413AB (Lambda Cygni) - 0.91", mags 4.7, 6.3 - "easy but fuzzy"  A combination of it being lower in the sky and a mirror in need of cleaning - the brighter pairs aren't very forgiving of either.  Kind of strange seeing it look nothing like the sketches from folks with smaller apertures; the secondary is very "well-fed" in my scope.
  • STT28 - 0.84", mags 7.6, 8.8 - a moderately unequal pair sitting nicely side by side
  • STF13 - 0.96", mags 7.0, 7.1 - "even, bright"  Definitely recommend this one if you're looking for a sub-arcsecond pair to try, provided you aren't too far south.

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#236 flt158

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Posted 30 September 2023 - 08:45 AM

 

Tonight was more of a carbon star night, but there's always a double or two along the way:

 

  • BU182 - 0.73", mags 8.7, 9.1 - "nicely dim, even, with ample space at 381x" 
  • STT413AB (Lambda Cygni) - 0.91", mags 4.7, 6.3 - "easy but fuzzy"  A combination of it being lower in the sky and a mirror in need of cleaning - the brighter pairs aren't very forgiving of either.  Kind of strange seeing it look nothing like the sketches from folks with smaller apertures; the secondary is very "well-fed" in my scope.
  • STT28 - 0.84", mags 7.6, 8.8 - a moderately unequal pair sitting nicely side by side
  • STF13 - 0.96", mags 7.0, 7.1 - "even, bright"  Definitely recommend this one if you're looking for a sub-arcsecond pair to try, provided you aren't too far south.

 

 

 

Tonight was more of a carbon star night, but there's always a double or two along the way:

 

  • BU182 - 0.73", mags 8.7, 9.1 - "nicely dim, even, with ample space at 381x" 
  • STT413AB (Lambda Cygni) - 0.91", mags 4.7, 6.3 - "easy but fuzzy"  A combination of it being lower in the sky and a mirror in need of cleaning - the brighter pairs aren't very forgiving of either.  Kind of strange seeing it look nothing like the sketches from folks with smaller apertures; the secondary is very "well-fed" in my scope.
  • STT28 - 0.84", mags 7.6, 8.8 - a moderately unequal pair sitting nicely side by side
  • STF13 - 0.96", mags 7.0, 7.1 - "even, bright"  Definitely recommend this one if you're looking for a sub-arcsecond pair to try, provided you aren't too far south.

 

Delightful report from you, Columbidae!

There are many fans of Lambda Cygni, as I am sure you are aware. 

I required 280x to see a black gap a few years ago.

Only recently did I split STF 13 (in Cepheus) at the same magnification. 

 

I'm sorry I haven't been reporting on double stars lately. 

I had set up my WO 158mm apo last night (Friday 29th October).  

But as soon as Sol setted, the dreaded high clouds arrived. bawling.gif

Even the full Moon was shrouded in this same cloud. 

 

2023 is definitely one of the worst for clear skies over here in Ireland. 

I've only had 28 observing sessions. 

 

If it's my God's will, clearer skies will return. 

 

And on that note, best regards from Aubrey.  


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#237 columbidae

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Posted 13 November 2023 - 07:09 PM

Seeing conditions last week (unlike the clouds this week) were decent, but I was surprised when I checked the separations on a few close pairs. 

 

  • BU393 - 0.67", mags 6.9, 8.4 - Pretty tough, but I'm unsure about this one; the last recorded observation in the WDS is from 1991, 32 years ago.  Anyone know of any other sources to crosscheck from?  (Or want to follow up with an observation of their own?) 
  • STT20AB - 0.63", mags 6.1, 7.2 - Grade 3 orbit in WDS, so it's pretty likely this is the correct separation. 
  • BU303 - 0.46", mags 7.3, 7.6 - This pair was an easier split than BU393 - I don't know if it's because of the smaller magnitude difference (didn't seem like it to my eyes) or what.  The last observation is from 2018, but there's not a whole lot of other information on this one in the WDS either, so who knows.
  • STT500 - 0.38", mags 6.1, 7.4 - This one has a Grade 4 orbit in the WDS catalog, so it's a bit more sure than the ones with few observations.  Still have a hard time personally believing it though; I didn't think the seeing was that good.  Maybe I'm getting better at picking out the pattern in the fleeting moments of calm.  There certainly weren't any picture perfect Airy disks this session.

 

Summer is definitely better here for good seeing, but between the bugs and the oppressive nighttime heat you definitely pay for it.


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#238 fred1871

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Posted 13 November 2023 - 08:51 PM

Thought I'd look up the numbers on BU 393 (00 18.3 -21 08). The 1991 measure turns out to be by Tycho, and is slightly aberrant from the probable true numbers. If you look up the 4th Interferometric Catalogue you'll find that other measures in the period were different - making it slightly closer than Tycho gives.

 

It's been a slowly widening pair as the WDS entry suggests. In 1989 Hartkopf with 4-metre scope and using speckle got 0.626" and 24.1 for PA. Hipparcos in 1991 found 0.624" and 24 for PA. Hartkopf again, two measures in 1991, separations 0.619" and 0.623". The small variations are from the usual slight errors of measuring, notably smaller than older methods such as bi-filar micrometer.

 

So the more accurate measure would be 0.62" for 1991. I've examined many hundreds of doubles measures in this period around the time of Hipparcos/Tycho measuring, and compared the often differing TYC and HIP numbers with speckle measures, which are numerous in the period from a deliberate program of measuring for comparison of satellite with ground-based measures. Where TYC and HIP differ, it's almost always that HIP is better for close matching of speckle measures, and Tycho also in a surprising number of cases is not consistent with the long-term trend, as evaluated (where possible) to include post-1991 measures.

 

For a more recent measure than 1991 I'd suggest checking for Gaia DR3 data, which would enable a calculation of separation and angle for the date of the Gaia measures, about 25 years after Hipparcos, to show if BU 393 continued to widen subsequently.


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#239 Nucleophile

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Posted 16 November 2023 - 01:09 PM

Seeing conditions last week (unlike the clouds this week) were decent, but I was surprised when I checked the separations on a few close pairs. 

 

  • BU393 - 0.67", mags 6.9, 8.4 - Pretty tough, but I'm unsure about this one; the last recorded observation in the WDS is from 1991, 32 years ago.  Anyone know of any other sources to crosscheck from?  (Or want to follow up with an observation of their own?) 
  • STT20AB - 0.63", mags 6.1, 7.2 - Grade 3 orbit in WDS, so it's pretty likely this is the correct separation. 
  • BU303 - 0.46", mags 7.3, 7.6 - This pair was an easier split than BU393 - I don't know if it's because of the smaller magnitude difference (didn't seem like it to my eyes) or what.  The last observation is from 2018, but there's not a whole lot of other information on this one in the WDS either, so who knows.
  • STT500 - 0.38", mags 6.1, 7.4 - This one has a Grade 4 orbit in the WDS catalog, so it's a bit more sure than the ones with few observations.  Still have a hard time personally believing it though; I didn't think the seeing was that good.  Maybe I'm getting better at picking out the pattern in the fleeting moments of calm.  There certainly weren't any picture perfect Airy disks this session.

 

Summer is definitely better here for good seeing, but between the bugs and the oppressive nighttime heat you definitely pay for it.

I should be able to give BU 393 a shot in the near future with my 8 inch reflector.  I have not observed this double as yet is seems.  I agree with Fred's analysis of the historical record.  Unfortunately, this double is an example of Gaia not detecting the secondary, so we don't have that (more recent) data point.  An independent measure is in order.  In the meantime, a comparative observation against congeneric candidates should shed some light.

 

According to my resolution calculator, BU 393 should remain unresolved when viewed on a night of good conditions (using my 8 inch instrument) if the separation is still around 0.62".  However, a rho value of 0.65" should be resolvable.  It will likely take several cracks at it to be certain.

 

STT 20AB has my interest as well.  Thanks for sharing these.

 

PS:  Gaia doesn't detect the companion for STT 20AB either.  I wonder if this is a part of the sky not scanned well by the satellite?


Edited by Nucleophile, 16 November 2023 - 06:28 PM.

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#240 Nucleophile

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Posted 12 December 2023 - 08:15 PM

As a follow up to my post above, I have made several observations of BU 393 using my 8 inch reflector as a means of trying to nail down the separation.  As mentioned previously, Gaia does not see the secondary for this double and a recent measure is lacking.  

 

To help solve the problem, I have found a good comparator:  BU 1052 in Orion.  It is likely many of you have viewed this double considering its proximity to the very interesting and complex multiple star Sigma Orionis.

 

The Tycho magnitudes for BU 1052 are 6.68 and 8.22; those for BU 393 are 6.90 and 8.42.  BU 1052 has an estimated separation of ~0.65" (grade 3 orbit).  The historical record for BU 393 suggests a value of ~0.62" (or a bit wider).

 

As best as I could, I observed these two double stars on the same night, albeit at different times to allow the Orion pair to rise to at least 50 degrees above the horizon.  BU 393 never rises more than 50 degrees above the horizon in my sky.  When observed on the same night, the pairs seemed very similar with respect to separation.

 

The clearest, high power view I had of BU 393 showed it (fleetingly) to be a snowman at 460x (3mm DeLite); the pair never resolved to two separate stars, but the correct position angle was unambiguously observed based (aided by the apparent magnitude difference).

 

Last March, I made numerous high power observations of BU 1052, the clearest of which showed the pair as two stars tangent (not split).  However, this was a singular instance; all other observations showed the pair as a snowman (i.e., not resolved to two stars).

 

And so I wait for a night of great seeing to further clarify the matter.  

 

I will endeavor to get a measure on BU 1052 this year and one on BU 393 next year.

 

If you are inclined, make a comparative observation of these two and let me know what you see.  smile.gif


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#241 Nucleophile

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Posted 17 December 2023 - 01:03 AM

Conditions were very good tonight for observing limit objects with my 8 inch reflector:  excellent transparency and very good seeing along with no wind and very little moonlight.  I was able to make a solid head to head observational comparison of BU 393 with BU 1052 (described in the post above).  The doubles were observed about 4 hours apart and always immediately after assuring thermal equilibrium of the reflector mirror.

 

BU 393

276x (Pentax 5XW):  very tight; notched asymmetric rod

345x (Tak TOE 4):  discs are ~half tangent and exhibit a delta mag of perhaps less than one

418x (Tak TOE 3.3):  when seeing permitted, image best described as discs 3/4 tangent--two photo-centers never seen

 

 

BU 1052

276x:  discs are half tangent and display obvious mag contrast

345x:  snowman shape; discs are almost tangent

418x:  just tangent; when seeing permitted two photo-centers could be seen, albeit fleetingly

 

So, I think BU 393 is just a bit tighter than BU 1052.  The estimated value of ~0.62" seems like a good number based on my observations.

Next thing to do is measure both of these doubles myself using my larger reflector.


Edited by Nucleophile, 17 December 2023 - 02:46 AM.

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#242 Nucleophile

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Posted 30 December 2023 - 02:08 AM

Tonight I observed the physical pair STT 51 with my 8 inch reflector.  The near equal magnitude stars (8.51 and 8.74 [Tycho]) are in the sweet spot for my reflector, and this allowed me to achieve a personal record for tightest resolution of a pair with this instrument.

 

Over the years, this binary has been slowly closing.  Attached is a screenshot of page 50 from Hussey's Micrometrical Observations of Double Stars Discovered at Pulkowa Observatory that shows the measures to date as of 1901.

 

     STT51_HusseyP50.jpg

 

On page 1396 of Burnham's Celestial Handbook [Vol. 3, published in 1978], the pair is listed with a separation of 0.9 arcseconds.  Curiously, Bruce MacEvoy did not include this double in the 2nd Ed. of the Cambridge Double Star Atlas; perhaps the definitive binary nature of the double was too uncertain at the time of publication (?)

 

A provisional grade 5 orbit has been calculated for the pair which gives a separation for the time of observation at ~0.46 arcseconds--this is far too tight based on my observations and the historical record.  From an examination of the Gaia satellite data (0.594") and the most recent measure from 2019 (0.57"; unknown source), I guesstimate the separation to be about 0.55"--just a bit below the Dawes threshold for my scope [0.57"].  

 

Above average seeing and excellent transparency with no wind afforded an opportunity to study the pair in detail using some new Japanese lenses, as follows:

 

197x (Pentax 7XW):  single yellow star

 

230x (Tak 6 TPL):  very slightly extended/a light yellow stubby rod; a sketch of the putative position angle against the drift-determined cardinal directions proved a solid match to that given in the literature (>350 degrees)

 

276x (Tak 12.5 TPL/PowerMate 2.5x):  an equal pair with a slight notch

 

345x (Tak 4 TOE):  a sharp image that showed a clear notch and a position angle running roughly north/south 

 

418x (Tak 3.3 TOE):  image starting to break down; when seeing allowed, the unresolved equal magnitude stars were seen as half tangent 

 

460x (Tak 6 TPL/TV 2x barlow):  a surprising sharp image; the two stars were almost resolved to two photo-centers

 

535x (Pentax 2.58XO): with careful fine focus and some patience, the pair was seen as resolved to two unique photo-centers three separate times; furthermore, the image showed [correctly] the star pointing nearly due south as the primary

 

If you have some clear skies and sufficient aperture I encourage you to give this Otto Struve double your attention--you won't be disappointed.


Edited by Nucleophile, 30 December 2023 - 03:51 AM.

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#243 flt158

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Posted 30 December 2023 - 08:41 AM

Hello Mark. 

You have given us a truly brilliant set of observations on STT 51!

Those with higher apertures can give this Perseus true binary a go. 

My limit is STF 1863 whose separation was 0.648 in 2022. 

 

Happy New Year to you and everyone here. 

 

From Aubrey. 


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#244 fred1871

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Posted 01 January 2024 - 08:40 PM

Regarding STT 51 in Perseus, discussed above:

QUOTE: On page 1396 of Burnham's Celestial Handbook [Vol. 3, published in 1978], the pair is listed with a separation of 0.9 arcseconds.  Curiously, Bruce MacEvoy did not include this double in the 2nd Ed. of the Cambridge Double Star Atlas; perhaps the definitive binary nature of the double was too uncertain at the time of publication (?)

 

I checked my 1st and 2nd Editions of the Cambridge Double Star Atlas (CDSA). What I found is that there's no bar (double indicator) through the tiny dot for STT 51. I think there's a mis-identification here, because nearby BU 1175 is shown with a bar through it. On the map, both editions, STT 51 is lower left from Kappa Persei, BU 1175 is lower right from it.

 

The matter of genuine binaries being included and supposed optical pairs being excluded is probably the biggest wrong decision made in CDSA 2nd Ed. The data at the time (pre-Hipparcos) was in many cases not adequate to decide if a pair was gravitational or line of sight. In the case of STT 51 it appears simply to be overlooked - no bar, despite PM numbers in the WDS suggesting very clearly gravitational rather than chance line-up. There are quite a few like this I've come across.

 

Curiously, despite eliminating optical pairs from the 2nd Edition, Bruce McEvoy in discussions here on CN agreed that the aesthetics of a pair was something real and of interest (legitimate observing perhaps :-)). So some striking combinations such as HJ 3945 in Canis Major were not described; likewise possibly non-binary doubles like Eta Orionis (DA 5) that are long-time favourites for observers were also excluded. I find the decision to bother with the distinction very surprising given that the CDSA is intended as an observer's manual.


Edited by fred1871, 02 January 2024 - 07:02 AM.

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#245 columbidae

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Posted 02 January 2024 - 05:22 AM

Been a little bit since my last post, so this covers five different nights in the last three weeks of December (separated by spaces). 

 

  • BU 84 - 0.98", mags 6.4, 7.9
  • STT 119 - 0.69", mags 8.1, 8.9
  • A 2724 - 0.85", mags 8.4, 9.2  notes: "close, moderately uneven" (though given some of the other doubles listed, you can tell I'm super consistent with my notes and impressions)
  • A 816 - 0.90" mags 7.5, 7.8
  • HU 1030 - 0.80" mags 8.9, 9.0
  • STT 6 - 0.66" mags 7.5, 8.8 - Together these form the primary of STF26, whose companion is a mag 9.9 star 13.1" away.
  • BU 1030 - 0.8" mags 7.8, 9.7

I was confused for a bit, because it seemed like I was struggling to make any of the usual splits, despite relative steadiness.  I eventually noticed that my mirror support had lost a fair number of the nylon(?) contact points and was kinda just catawampus with one of the whiffle supports basically not engaged at all.  Some creative fixes later and I come out with this that night:

  • BU 98 - 0.63" mags 8.3, 8.4
  • STF 1074 - 0.8" mags 7.4, 7.8
  • STF 1126 - 0.8" mags 6.6, 7.0
  • STT 182 - 0.92" mags 7.8, 7.9
  • HO 245 - 0.67" mags 7.9, 8.7
  • STF 1157 - 0.67" mags 7.9, 7.9
  • A 539 - 0.66" mags 8.8, 9.5
  • STF 787 - 0.63" mags 8.3, 8.8
  • STF 849 - 0.94" mags 9.2, 9.5

I still need to address the cracked weld in the edge support, but it doesn't seem that that was causing any issues (yet) at least. 


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#246 Nucleophile

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Posted 02 January 2024 - 11:09 AM

Nice report and list of targets, Columbidae. 

 

BU 98 is one that has given me fits over the years with my 8 inch reflector.  I look forward to tackling it again this season.

 

Need to check in on STF 787 also...



#247 fred1871

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Posted 02 January 2024 - 11:07 PM

Columbidae, in #237 above you have observing notes on STT 500 (in Andromeda):

QUOTE:

STT500 - 0.38", mags 6.1, 7.4 - This one has a Grade 4 orbit in the WDS catalog, so it's a bit more sure than the ones with few observations.  Still have a hard time personally believing it though; I didn't think the seeing was that good.  Maybe I'm getting better at picking out the pattern in the fleeting moments of calm.  There certainly weren't any picture perfect Airy disks this session.

 

I don't know where you found the separation of 0.38" because the most recent measure in the WDS, 'Last Precise', is for 2018 at 0.483" and PA 020. This fits with the two older measures I found in the 4th Interferometer catalogue:

McA   1976  0.515"   356 

Pru     2012  0.460"   011

L.P.    2018   0.483"   020

None of these measures suggest anything near 0.38".

Therefore, your surprise over getting a split seems likely due to the pair being wider than expected.  Of course it's still very sub-arcsecond :-)

 

In your more recent notes in #245 above, is the second list (basic data, no observing notes) to be read as Mark did, a list of objects to try next? I'm asking because sometimes you list a double without observing notes while indicating that you have observed it. And the magnification is usually 381x as you said to Aubrey? Thanks.



#248 fred1871

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Posted 02 January 2024 - 11:23 PM

Mark, regarding BU 98 in Monoceros, that you mention as a problem object (#246)

To quote: BU 98 is one that has given me fits over the years with my 8 inch reflector

 

Looking through my observing notes, I found I have one observation of it recorded, in January 2021.

This was with my Mewlon 210, where I recorded it was barely separated at 240x (10mm XW), and I thought the view improved at 270x (9mm Delite) and better again at 345x (7mm XW), the latter I described as a neat very close split; nice object, a rather good white pair if the seeing allows.  

 

It's effectively an object for a Dawes split, given the near-equal magnitudes (which I noted at the time). But as always with the very close pairs it will depend on the atmosphere at the time of observing, so I expect you've had bad luck with seeing conditions when you've tried it. The WDS Last Precise gives a separation for 2016 of 0.634", not much different from Hipparcos in 1991 at 0.650".



#249 columbidae

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Posted 03 January 2024 - 12:00 AM

Columbidae, in #237 above you have observing notes on STT 500 (in Andromeda):

QUOTE:

STT500 - 0.38", mags 6.1, 7.4 - This one has a Grade 4 orbit in the WDS catalog, so it's a bit more sure than the ones with few observations.  Still have a hard time personally believing it though; I didn't think the seeing was that good.  Maybe I'm getting better at picking out the pattern in the fleeting moments of calm.  There certainly weren't any picture perfect Airy disks this session.

 

I don't know where you found the separation of 0.38" because the most recent measure in the WDS, 'Last Precise', is for 2018 at 0.483" and PA 020. This fits with the two older measures I found in the 4th Interferometer catalogue:

McA   1976  0.515"   356 

Pru     2012  0.460"   011

L.P.    2018   0.483"   020

None of these measures suggest anything near 0.38".

Therefore, your surprise over getting a split seems likely due to the pair being wider than expected.  Of course it's still very sub-arcsecond :-)

 

In your more recent notes in #245 above, is the second list (basic data, no observing notes) to be read as Mark did, a list of objects to try next? I'm asking because sometimes you list a double without observing notes while indicating that you have observed it. And the magnification is usually 381x as you said to Aubrey? Thanks.

0.48" is way more likely than 0.38" for STT 500 based on how the split felt to observe - I naively pulled the number from the entry on Stelle Doppie, under the orbital elements section's table for the year 2023.  I'm assuming that it's in error (though what kind, I'm unsure.)  (This is just another step for me down the dark path towards speckle-interferometry).

 

The second list from post #245 were the sub-arcsecond doubles I observed on the night I fixed my mirror support.  Given that they were mostly fairly even and otherwise non-superlative, I didn't have much to note about them during observation.  (I may have been rushing.)  I use 381x for these sub-arcsecond pairs almost without exception.  287x (my 7mm with the barlow element screwed into the bottom) could work, but it's a rare night where I can use that power but not 381x (for doubles at least).  Even if the seeing is 8+/10, I typically don't go any higher (572x, 762x) due to very diminishing returns in my non-premium, undriven scope.



#250 Nucleophile

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Posted 03 January 2024 - 02:54 AM

A good discussion regarding some challenging sub-arcsecond objects.   Fred, I remember well our conversation last year re: BU 98.  With some persistence while waiting for the right conditions, I did eventually have success.  I have a few new lenses in my arsenal to give it another go on a similarly steady night--but it will be another month or so before the object is preferentially placed.  That is one of the great things about double stars--they are like old friends you get to visit with year after year.  And, like people, they are prone to change over time.

 

 

Columbidae:  I have also had issues in the past with my larger reflector--goes with the territory sometimes for the benefit of greater light grasp.  I love my reflectors and wouldn't have it any other way.  All machines need maintenance for optimal performance.

 

Despite the delta mag, the Otto Struve double in AND that is mentioned above (STT 500) is another sort of challenging double I have actually had a fair amount of success with in the past year with my 8 inch reflector--in this case, a positive result being more in line with detection of duplicity (versus resolution) with correct assignment of position angle, the ease of which is aided by the differing stellar magnitudes.


Edited by Nucleophile, 03 January 2024 - 03:29 AM.



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